Coenzyme Q10 corresponds to ubiquinones (formula: C59H90O4; molecular weight: 863.4) that is 2,3-dimethoxy-5-methyl-6-polyprenyl-1,4-benzoquinone with a side-chain comprising 10 isoprene units, and existing in higher animal. It is one kind of coenzyme Q known as ubidecarenone or coenzyme Q10. The physical property of coenzyme Q10 is known as orange crystal, which is a fat-soluble substance having melting point at about 49° C. Coenzyme Q10 is known as not only a coenzyme having biological activity but also a vitamin-like active substance having function of improving oxygen utilization efficiency. Coenzyme Q10 is considered to be essential in production of adenosine triphosphate in mitochondria, and it is reported to be effective for the treatment of cardiac disease, hypertension, rheumatic valve affection or inflammation of alveolar each by improving its immune function. It is also employed for the treatment of congestive heart failure or cerebrovascular disorder, for prevention of adverse effects of anticancer agents (prevention of cardiopathy by adriamycin), for fatigue reactivation, for energy activation, and for antioxidation of in vivo active oxygen. Its validity to prevent from aging employed as skin external preparation is expected, too. Thus, coenzyme Q10 has high bioactivity and it is believed as highly safe substance existing in vivo.
In late years, various kinds of technology are disclosed regarding coenzyme Q10 under such situations.
For example, JP-A-60-199814 discloses a fatty emulsion obtained by processing nonionic surfactant such as polyethylene glycol, hardened castor oil polyoxyethylene-(20)-ether and so on with Manton Gaulin type high pressure homogenizer (500 to 550 kg/cm2).
JP-A-63-150221 discloses an emulsified composition for pharmaceutical medicines with excellent absorbency obtained by employing ubiquinone as crystalline agent, dissolving it into adipic acid or an oil such as soybean oil and so on in supersaturated condition, preparing O/W type microemulsion with the use of surfactant such as polyoxyalkylene base, polyglycerol fatty acid ester, Tween base or so, and by adding another O/W type microemulsion.
EP-494651B1 and U.S. Pat. No. 5,298,246 disclose a composition with improved absorbency prepared by dissolving ubiquinone into oil, emulsifying with the use of a fat globule membrane in mammals milk, and by fractionating particles of specified particle diameter (1-5 μm).
JP-A-2000-212066 discloses aqueous emulsion containing fat-soluble substance prepared by combining ubiquinone as lipid-soluble substance, polyglycerol fatty acid ester as emulsifier and glycerol-phosphoric lipid, further adding polyalcohol and water, and then stirring, followed by homogenization processes with high pressure of 500-2000 kg/cm2.
Coenzyme Q10 fat emulsion described in JP-A-60-199814 has problems that its particle size is large and that it is inferior in transparency.
The composition disclosed in EP-494651B1 and U.S. Pat. No. 5,298,246 wherein coenzyme Q10 is necessarily dissolved in oil has problems that its particle diameter is large and that it is inferior in transparency. Besides, there is problem that it is inferior in heat resistance, acid resistance and salt-resistance each needed for manufacturing foods and beverages.
JP-A-63-150221 further teaches cosmetic liquid that is superior in storage stability under low temperature, however in this technology, transparency becomes poor and precipitation occurs along with decrease of the liquid temperature, and there is problem that it is inferior in heat resistance, acid resistance and salt-resistance each needed for manufacturing foods and beverages.
JP-A-2000-212066 also teaches oil-in-water type microemulsion applicable to various kinds of oily substances. However, this technology has problems of being inferior in acid resistance, salt-resistance and heat resistance under various conditions.
JP-A-9-168369 discloses a solubilized oil and fat composition containing polyglycerol fatty-acid ester, water and food additives. However, the composition has problems of being inferior in transparency and stability.
A water-soluble composition containing coenzyme Q10 is expected to satisfy the following requirements:    (1) small particle sizes, and superior in transparency;    (2) high concentration of coenzyme Q10 without needing oil components for dissolving or dispersing;    (3) superior in a feeling of delicious dining and taste;    (4) without needing special conditions or complicated processes in manufacturing; and    (5) superior acid-proof heat resistance and salt-tolerant heat resistance which are necessary for addition into various food.
However, formulation of coenzyme Q10 by emulsification is generally accompanied by difficulty because coenzyme Q10 is insoluble in water, instable against light, heat or alkali, and high crystallinity. Further, even once after preparing emulsion, the problem that separation, deposition, precipitation or floating will occurs by the re-crystallization of coenzyme Q10. Although the concentration of coenzyme Q10 in water-soluble compositon is needed to increase to get sufficient effect of coenzyme Q10, it is difficult to aqueously solubilize because of its dissolution retardency and high crystallinity.
Moreover, a solubilized solution without requiring an ordinary oily component in an occasion of adding coenzyme Q10 in foods and beverages, cosmetics or so; superior in transparency, acid resistance, salt-resistance and heat resistance that are altogether necessary when blending with the foods and beverages, cosmetics or so; excellent in emulsion stability and storage stability; further capable of containing coenzyme Q10 with high concentration was eagerly demanded. Still further, improving absorbency of coenzyme Q10 was also demanded because the in vivo absorbency was poor.
Accordingly, the present invention has an object of overcoming the above problems and providing a water-soluble composition containing coenzyme Q10 and a process for producing thereof without employing solvent such as oils, superior in storage stability such that coenzyme Q10 will not precipitate, deposit or float during a long term preservation, also superior in texture, taste, acid resistance, salt-resistance, heat resistance in an occasion of addition into medicines, foods and beverages, cosmetics and feeds; and further improving bioabsorbency conspicuously. Another object of the invention is to provide medicines, foods and beverages, cosmetics and feeds together with their administration superior in transparency even after blending the composition into them without deposition, precipitation, or floating of coenzyme Q10.